Master of Science I (Electronics Science) Examination:
Oct Nov 2016 Semester II (Old CGPA)
SLR No. Day
Date Time Subject Name Paper
No. Seat No.
SLR SJ
345
Thursday
17/11/2016
10:30 AM
to
01:00 PM
Modern Antenna Design
C
V
Instructions: Q. No.1 and 2 are compulsory.
Answer any three questions from Q.No.3 to Q.No.7.
All questions carry equal marks.
Total Marks: 70
Q.1 Objective Questions. 14
Select correct alternatives: 08
An antenna behaves as a resonator circuit only when its length is:
λ λ/4
λ/2 or its integral
multiple
None of the above
The directivity of an isotropic antenna is
Zero Less than unity
Unity Infinity
A half wave dipole produces
A figure pattern A broadside pattern
An end-fire pattern None of the above
Electrical length or effective length of an antenna.
Greater than its physical
length
Smaller than its physical length
Equal to its physical length None of the above
The simplest parasitic array comprises of
Two elements Three Elements
Five elements None of the above
In an end-fire array
Maximum reception is along the axis
Maximum reception is perpendicular to the axis
Directional pattern is bi-directional
None of these
Which one of the following terms does not apply to the Yagi-Uda array
Good bandwidth Parasitic elements
Folded dipole High gain
Page 2 of 2
Which of the following antenna is best excited from a waveguide?
Biconical Horn
Helical Discone
State True or false: 06
The radiation patterns of vertical and horizontal dipoles are identical.
Effective area of an antenna is a function of frequency.
Radiation beam in broadside array is along the axis of the array.
Ideally, reflector size is infinitely large.
Cassegrain feed is best suited for low noise receiver applications.
Antenna gain is inversely proportional to beam width.
Q.2 Answer the following: 14
Discuss about the term "Radiation Patter". 05
Write a short note on operation of Yagi Uda array. 05
Explain the principle of pattern multiplication 04
0
Q.3 Explain the following terms with respect to antenna:
Radiation intensity ii) Directivity
iii) Beam efficiency iv) Gain
08
What do you understand by effective height and radiation resistance of an
antenna?
06
Q.4 Obtain expressions for the far field and power radiated by a half wave
antenna and calculate the radiation resistance of the antenna.
08
Prove that radiation resistance of half wave dipole is 73Ω. 06
Q.5 What is an antenna array factor? Derive an expression for array factor for
end-fire array consisting of isotropic elements.
10
Give the concept of 'Antenna array scanning. 04
Q.6 Describe in detail the Cassegrain method of feeding a paraboloid reflector
with the help of geometry of this feeding arrangement.
08
With a neat diagram, explain the operation of a folded antenna. 06
Q.7 Explain the principle of measuring the radiation pattern of the antenna. 08
Write a note on pyramidal horn antenna with design equations. 06